Investigation of breed and sex effects on cytochrome P450 gene expression in cattle liver.

Abstract Many cytochrome P450 enzymes are involved in xenobiotic metabolism and elimination. In humans, genetic variation in some of these enzymes contributes to inter-individual drug responses, sometimes having significant clinical effects. Transcript levels of eight P450 genes were evaluated in liver to investigate potential differences in breed and sex in cattle. In Angus calves, heifers appeared to have higher gene expression than steers for two of the eight genes. In Angus and Simmental pregnant cows, Angus appeared to have higher gene expression for three of the eight genes. Transcript evaluation is just the first step toward determining if differences exist between breeds and sexes in enzyme catalytic activity. However, others ( Giantin et al., 2008 ) have shown correlations between transcript levels and catalytic activity in other cattle breeds. Therefore breed and/or sex of an animal may need to be considered before administering a dose of a xenobiotic due to the potential for harmful drug residues in foodstuffs as well as improper treatment of disease conditions.